In recent years, the integration degree of semiconductor devices has risen remarkably. The increase of the integration degree is sustained by advances in process techniques. Especially, advances in photolithography techniques and dry etching techniques play a great role for the rise of the integration degree. In recent dry-etching techniques, a tendency can be observed toward the active use, from the view point of miniaturization, of a low gas pressure, high density plasma. Considering such a background, dry-etching apparatus using an electron cyclotron resonance plasma, an inductive coupling type plasma or a helicon wave excitation plasma have been developed and sold (see for example: "Semiconductor World" Oct. issue 1993, pp. 68-75).
Below, an example for a conventional oxide film etching apparatus is explained with reference to FIG. 1, which shows an apparatus using an inductive coupling type plasma.
In FIG. 1, numeral 1 is an induction coil and numeral 2 is a high frequency power source, which supplies the induction coil 1 with high frequency electricity. Numeral 3 is a lower electrode and numeral 4 is a high frequency power source, which supplies the lower electrode 3 with high frequency voltage. Numeral 5 is an upper silicon electrode and numeral 6 is a silicon substrate placed on the lower electrode 3 and arranged in parallel to the upper silicon electrode 5 within at reaction chamber 7. Numeral 8 is a pressure control valve and numeral 9 is an exhaust pump, by which a predetermined pressure is maintained in the reaction chamber 7. Numeral 10 is a gas bottle, supplying C.sub.2 F.sub.6 to the reaction chamber 7 through a mass flow 13. Numeral 11 is a heater, which maintains the upper silicon electrode 5 at a constant temperature. Numeral 12 is a silicon ring, which is arranged to enclose the silicon substrate 6 on the lower electrode 3. Numeral 13 is a mass flow and numeral 14 is a matcher to attain impedance matching between the high frequency power source 4 and the lower electrode 3.
C.sub.2 F.sub.6 is introduced into the reaction chamber 7 from the gas bottle 10 and maintained at a predetermined pressure. A plasma is generated in the reaction chamber 7 by supplying the induction coil 1 with high frequency electric power from the high frequency power source 2. Ions from the plasma are attracted by impressing a bias voltage onto the lower electrode 3 with the high frequency power source 4, so that the silicon substrate 6 is etched.
The silicon ring 12 and the upper silicon electrode 5 (which are referred to as silicon members below) realize a high etching speed ratio of the oxide film against the silicon substrate 6 by decreasing the fluorine in the plasma due to a reaction with silicon (see FIG. 2 B). This silicon member has a smooth surface, and as is shown in FIG. 3B, the average roughness of the irregularities H of the surface is about 0.1 .mu.m.
Numeral 15 of FIG. 4 is an example for the relationship between operating time T and selectivity ratio R for the etch rate of the oxide film of the silicon substrate with respect to the resist, when conventional silicon members with a smooth surface are used.
A constant time period is necessary so that the silicon members can scavenge halogen elements. After such aging is finished, a stable etch rate is attained.
However, as can be gathered from numeral 15 of FIG. 4, in a conventional manufacturing apparatus using silicon members with a smooth surface, a long period of time is necessary to stabilize the selectivity ratio R for the etch rate of the oxide film with respect to the resist. That means, there was the problem that a long aging time is necessary to put the silicon members into a condition where they can scavenge halogen elements.